Core metal inserts for weatherseals generally are known. Various examples of core metal inserts are described in, e.g., U.S. Pat. Nos. 5,783,312, 5,871,682 and 6,079,160, the contents of each of which are incorporated herein by reference. The metal insert typically is coated or encapsulated by a suitable flexible material and bent to an appropriately shaped longitudinal contour to provide a particular weatherseal. The weatherseal has a longitudinally extending channel-shaped portion for gripping flange joints such as those that extend around openings in motor vehicles. The metal insert is provided in the weatherseal so that when bent into a channel (U-) shape cross-section, the embedded insert provides strength for gripping the flange joint to hold the weatherseal in place. The weatherseal can be fitted to an associated door or door frame, window or window frame, or other installation where it is desirable to provide a seal between an openable contrivance and its frame in the closed position.
To provide the above-mentioned flexible material over the metal insert, the insert is drawn through a coating extruder where a coating of such material is applied. Generally, the material is an elastomeric material, such as a natural or synthetic rubber or flexible foam, and is applied in an uncured or softened state over the metal insert. Following extrusion, the coating is caused or permitted to dry or cure, at which point the coating material becomes bound to the metal insert over their interfacial contact area.
During the process for manufacturing a weatherseal, the metal insert is made in part by lengthening a sheet metal blank, and is drawn through the coating extruder in tension. The coating material applied over the insert typically is cured or dried while the insert remains in tension. Conventionally, once the tension on the insert is released, the insert has a contractile tendency that causes it to contract from its lengthened state while embedded in the extrusion coating. This can result in at least two negative effects. First, contraction of the insert can cause the weatherseal to warp, meaning that it becomes curved undesirably, making it less able or unable to mate to the surface or flange to which it was designed to be fitted. Second, contraction of the insert can cause it to become detached from the flexible material coating over their interfacial contact area. Depending on the geometry of the insert, as well as other unpredictable factors, this insert-to-coating separation can occur at numerous unpredictable locations over the contact area. As a result, the insert can become freed to move independently of the coating at these locations, which can result in abrasion of the coating material by the metal insert over time (e.g. resulting from repeated shutting of a door). As the coating material becomes increasingly degraded through abrasion, the seal provided by that coating can be compromised, contributing to premature failure of the weatherseal.